Sludge centrifuge

ABSTRACT

The centrifugal rotor has a level-maintaining outlet for cleanseparated liquid, a peripheral outlet at the greatest radius of the inside of the rotor wall, and a conical screw operable in the rotor to convey separated sludge for discharge from a region of the rotor remote from said outlets. A valve coacting with the peripheral outlet is associated with control means operable by the action of liquid discharged from the level-maintaining outlet to maintain the valve in condition to close the peripheral outlet, the valve being operable in response to interruption of the liquid discharge from the level-maintaining outlet to open the peripheral outlet and thereby effect removal of deposits on the conveyor screw.

Nilson et al.

Jan. 7, 1975 SLUDGE CENTRIFUGE Inventors: Carl-Goran Nilson, Tullinge;Sven 010v Olsson, Farsta, both of Sweden Alfa-Lavel AB, Tumba, SwedenMar. 22, 1974 Assignee:

Filed:

Appl. No.1

Foreign Application Priority Data Mar. 22, 1973 Sweden 40263/73References Cited UNITED STATES PATENTS 2/1932 Fawcett 233/20 R 8/1933Fawcett.... 233/20 R 6/1966 Barger 137/204 X 12/1970 Freeman et al137/810 FOREIGN PATENTS OR APPLICATIONS 902,500 12/1944 France 233/7Primary E.\'uminer-George H. Krizmanich Attorney, Agent, or FirmCyrus S.Hapgood [57] ABSTRACT The centrifugal rotor has a level-maintainingoutlet for clean-separated liquid, a peripheral outlet at the greatestradius of the inside of the rotor wall, and a conical screw operable inthe rotor to convey separated sludge for discharge from a region of therotor remote from said outlets. A valve coacting with the peripheraloutlet is associated with control means operable by the action of liquiddischarged from the level-maintaining outlet to maintain the valve incondition to close the peripheral outlet, the valve being operable inresponse to interruption of the liquid discharge from thelevelmaintaining outlet to open the peripheral outlet and thereby effectremoval of deposits on the conveyor screw.

5 Claims, 4 Drawing Figures F'ATENTEU JAN 1 5 SHEET 1 or 2 Fig. 2

PATENTED N 1 ms SHEET- 2 BF 2 SLUDGE CENTRIFUGE The present inventionrelates to a sludge centrifuge equipped with a liquid-level-maintainingoutlet for clean-separated liquid as well as with a conical screwcoaxial with the centrifuge rotor and feeding separated sludge to anoutlet located closer to the axis of rotation of the centrifuge rotorthan said liquid outlet, the cen trifuge also having an outlet which canbe opened intermittently and is located at the greatest radius of theinside of the wall of the centrifuge rotor. A centrifuge of this kind isdisclosed in the Swedish patent specification 310,624.

A centrifuge of the above-mentioned kind is of special interest for theseparation of a sludge-containing liquid which, in addition to sludgewith a higher specific gravity than the liquid, contains sludge with alower specific gravity than the liquid. As in the case of certain wastewaters, this lighter sludge may consist of sticky substances, such asfat, which deposit on the screw and fill its threads, whereby a furtherrunning of the centrifuge is made impossible. By opening the outletswhich can be opened intermittently and interrupting the supply of theliquid to be separated, but otherwise allowing the centrifuge to run,the rotor can be emptied of liquid through these outlets. After theliquid has discharged from the rotor, the deposits on the screw arethrown outwardly by the centrifugal force and fed by the screw to thesludge outlet.

In the centrifuge according to the Swedish patent specification 310,624,it is necessary for removal of deposits on the screw to take steps toopen the outlets through which the rotor is emptied of liquid, inaddition to an interruption of the supply of the liquid to be separated.The present invention relates to an improvement of this centrifugewhereby the discharge of liquid from the rotor is effected automaticallyby an interruption of the supply to the centrifuge of the liquid to beseparated. Consequently, in this way an appreciable simplification ofthe operation of the centrifuge is effected. More exactly, the newcentrifuge is characterized by a valve inserted in said outlet which canbe opened intermittently, said valve being arranged to be kept closedunder the action of liquid discharged from the levelmaintaining outlet.

A number of different embodiments are possible within the scope of thepresent invention. A first such embodiment is characterized in that thevalvecontrolled outlet has a radially outer opening forming.

a valve seat and that a double-armed lever, arranged on the outside ofthe centrifuge rotor, is journalled so that a valve body carried by oneend of the lever is movable radially relatively to said valve seat, theother end of the lever being arranged to be actuated by liquiddischarged from the level-maintaining outlet.

A second embodiment is characterized in that the valve-controlled outlethas a radially outer opening forming a valve seat for a radially movablevalve body and that a channel, provided with a drainhole, leads from thelevel-maintaining outlet to the radially outer end of the valve body.

A third embodiment is characterized in that the valve-controlled outletopens into a vortex fluidistor, located radially outside this outlet,the tangentially arranged inlet for the control liquid of the fluidistorcommunicating with the level-maintaining outlet.

A fourth embodiment is characterized in that the valve-controlled outlethas an axially directed, outer opening forming a valve seat for a valvebody which is axially movable in a chamber as a piston, the chamber thushaving an axially inner and an axially outer end, there being a channelleading from the levelmaintaining outlet to the outer end of thechamber, and each end of the chamber being provided with a drainhole.

The invention is described more in detail below with reference to theaccompanying drawings in which FIGS. 1 through 4 are axial sectionalviews of parts of four different embodiments, chosen by way of example,of the rotor of the present centrifuge. Corresponding details in thedifferent figures have the same reference numerals.

In FIG. 1, reference numeral 1 designates a centrifuge rotor having ahorizontal axis of rotation 2. A conventional conical screw 3 feedssludge, deposited on the inside of the rotor, to the left to the usualoutlet (not shown) which is located closer to the axis of rotation thanan outlet 4 for clean-separated liquid. The liquid to be separated issupplied through the usual inlet (not shown). The outlet 4 is formed bya hole located eccentrically in a disc 5 which is inserted in therighthand end wall of the rotor and which is adjustable by beingrotated. Thus, the distance of the liquid outlet 4 from the axis ofrotation 2 can be varied in a desired manner. At the greatest radius ofthe inside of the rotor there is a hole 6 passing radially through therotor wall. A double-armed lever 7 is journalled on a bracket on theoutside of the rotor wall. The left-hand end of the lever carries avalve body 8, the hole 6 opening into a valve seat for the valve body 8.The right-hand end of the lever has the shape of a scoop 9, whichcatches liquid discharging from the overflow outlet 4. As will bereadily understood, the valve 6, 8 is kept closed as long as liquiddischarges through the overflow outlet 4 (i.e., as long as rotor lcontinues to receive a supply of the liquid to be separated).

When it is desired to clean the screw 3, the liquid supply to the rotoris interrupted without the centrifuge being stopped. Liquid then ceasesto act upon the scoop 9, and the valve 6, 8 opens under the pressure ofthe liquid 10 present in the rotor. The latter is then emptied of allliquid through the hole 6, and the fat or similar sticky, light materialstuck in the threads of screw 3 is thrown from the latter by centrifugalforce and hits the inside of the rotors peripheral wall, whence thescrew feeds the material to the sludge outlet. After this cleaning hastaken place, the supply to the rotor of the liquid to be separated isresumed, the supply rate appreciably exceeding the discharge rate whichis possible through the hole 6.

In FIG. 2, ll designates an annular chute arranged on the outside of theend wall and catching a part of the liquid discharging from the overflowoutlet 4. The main part of the liquid from the outlet 4 flows. over theedge of the chute II. A channel 12 leads from this chute to the radiallyouter end of a radially guided valve body 13, for which the hole 6serves as a valve seat. The channel 12 has a drain hole 14. A recess 16is provided in the annular member 15 in which the channel 12 and chute11 are formed. As long as the supply of the liquid to be separated isuninterrupted, the valve 6, 13 is kept closed by means of the liquidpressure acting against the radially outer end of the valve body 13.When the supply of the liquid to be separated is interrupted, the supplyof liquid to the chute ll ceases and the channel 12 is emptied of liquidthrough the drain hole 14. The valve body 13 is thus thrown radiallyoutwards by the centrifugal force, the liquid being discharged throughthe hole 6 and the recess 16. The screw 3 therefore becomes cleaned, aspreviously described.

FIG. 3 shows a variation of the embodiment according to FIG. 2, in thatthe valve body in FIG. 2 has been replaced by a vortex fluidistor whosecavity 17, as seen in radial direction, has a circular shape. Thechannel 12 opens tangentially into the fluidistor, as indicated at 18,and supplies control liquid from the chute 11. As long as control liquidis supplied to the fluidistor from the chute 11, the whirl formation inthe fluidistor cavity 17 generates such a great flow resistance againstdischarge of liquid through the hole 6 that the outflow through thelatter is small. However, as soon as the supply of the liquid to beseparated is interrupted, the chute 11 is drained through the passagel2, l8, l4, whereupon the whirl movement in cavity 17 ceases and theflow resistance in the passage 6, 17, 14 is strongly reduced so that thecentrifuge rotor l is emptied through the hole 14.

In FIG. 4, l9 designates a valve housing secured to rotor 1 and in whichthere is arranged an axially movable valve body 20 provided with alabyrinth sea]. In the rotor end wall there is arranged an axial channel21 in which a tube 22 is inserted, this tube serving as a valve seat forthe valve body 20. The chute 11 is like the chutes 11 in FIGS. 2 and 3.The space 23 in which the valve body 20 moves has a liquid inlet 24 fromthe chute l1 and two drain holes 25 and 26, one at each end of the space23. As long as liquid flows into the space 23 from the chute 11, thevalve 20 22 is kept closed, since the right-hand end of the valve body20 has a greater surface area acted upon by liquid than its left-handend. However, as soon as the supply of liquid from the chute l1 ceases,the valve body 20 is pressed to the right and the liquid 10 is emptiedthrough the drain hole 25.

It will be understood that screw 3 is rotated at a different speed thanthe rotor l, in order to convey the separated sludge to the left towardthe sludge outlet. Those details of the centrifuge not illustrated arewell known in the art, as disclosed, for example, in U.S. Pat. Nos.3,447,742 and 3,506,187 dated June 3, 1969, and Apr. 14, 1970,respectively.

We claim:

1. In a sludge centrifuge, the combination of a centrifugal rotor forreceiving a sludge-containing liquid to be separated, the rotor beingmounted for rotation about an axis and having a liquid-level-maintainingoutlet for clean-separated liquid, the rotor also having a peripheraloutlet located at the greatest radius of the inside of the rotor wall, aconical screw mounted in the rotor coaxially thereof and operable toconvey separated sludge for discharge from the rotor at a region thereofremote from said outlets, a valve coacting with said peripheral outletfor opening and closing the same, and control means associated with saidvalve and operable by the action of liquid discharged from saidlevelmaintaining outlet to maintain the valve in condition to close saidperipheral outlet, said valve operating to open said peripheral outletin response to interruption of the liquid discharge from thelevel-maintaining outlet.

2. The combination of claim 1, comprising also a seat for said valve andat least partly defining said peripheral outlet, said control meansincluding a doublearmed lever mounted on the outside of said rotor andcarrying said valve on one arm of the lever, the other arm of the leverbeing in position to be actuated by liquid discharged from thelevel-maintaining outlet.

3. The combination of claim 1, comprising also a seat for said valve andlocated at the outer end of said peripheral outlet, said valve beingmovable radially to and from said seat and having a radially outer end,said control means forming a channel provided with a drain hole andleading from the level-maintaining outlet to said outer end of thevalve.

4. The combination of claim 1, in which said control means include avortex fluidistor located radially outside said peripheral outlet andinto which said peripheral outlet opens, the fluidistor having agenerally circular cavity and a passage leading from thelevelmaintaining outlet and opening tangentially into said cavity.

5. The combination of claim 1, comprising also a seat for said valve andthrough which said peripheral outlet opens in a direction parallel tosaid rotation axis, said control means forming a chamber in which thevalve is reciprocable parallel to said axis, said chamber having aninner end adjacent said peripheral outlet and having an outer end remotefrom the peripheral outlet, said control means also forming a channelleading from the level-maintaining outlet to said outer end of thechamber, each end of said chamber having a drain hole.

1. In a sludge centrifuge, the combination of a centrifugal rotor forreceiving a sludge-containing liquid to be separated, the rotor beingmounted for rotation about an axis and having a liquid-level-maintainingoutlet for clean-separated liquid, the rotor also having a peripheraloutlet located at the greatest radius of the inside of the rotor wall, aconical screw mounted in the rotor coaxially thereof and operable toconvey separated sludge for discharge from the rotor at a region thereofremote from said outlets, a valve coacting with said peripheral outletfor opening and closing the same, and control means associated with saidvalve and operable by the action of liquid discharged from saidlevel-maintaining outlet to maintain the valve in condition to closesaid peripheral outlet, said valve operating to open said peripheraloutlet in response to interruption of the liquid discharge from thelevel-maintaining outlet.
 2. The combination of claim 1, comprising alsoa seat for said valve and at least partly defining said peripheraloutlet, said control means including a double-armed lever mounted on theoutside of said rotor and carrying said valve on one arm of the lever,the other arm of the lever being in position to be actuated by liquiddischarged from the level-maintaining outlet.
 3. The combination ofclaim 1, comprising also a seat for said valve and located at the outerend of said peripheral outlet, said valve being movable radially to andfrom said seat and having a radially outer end, said control meansforming a channel provided with a drain hole and leading from thelevel-maintaining outlet to said outer end of the valve.
 4. Thecombination of claim 1, in which said control means include a vortexfluidistor located radially outside said peripheral outlet and intowhich said peripheral outlet opens, the fluidistor having a generallycircular cavity and a passage leading from the level-maintaining outletand opening tangentially into said cavity.
 5. The combination of claim1, comprising also a seat for said valve and through which saidperipheral outlet opens in a direction parallel to said rotation axis,said control means forming a chamber in which the valve is reciprocableparallel to said axis, said chamber having an inner end adjacent saidperipheral outlet and having an outer end remote from the peripheraloutlet, said control means also forming a channel leading from thelevel-maintaining outlet to said outer end of the chamber, each end ofsaid chamber having a drain hole.